David Cameron was audibly frustrated as he was given a thorough grilling this morning - even making an exasperated off-mic gaffe at the end of the interview.

After being given an easy ride by Sky's Eammon Holmes and LBC's Nick Ferrari, the Prime Minister was hauled over the coals by the BBC's Mishal Husain on the Today Programme over cuts to tax credits, Syria, ISIS and more.

After a tense exchange over the future of Syrian President Bashar al-Assad , the PM was heard exhaling sharply.

The nightmare interview started with Husain pressing Cameron on whether the hard working people whose side the Prime Minister claims to be on will end up worse off under Tory rule.

Presented with his own Chancellor's admission that 10% of working families will lose income after the Conservatives remove their tax credits, Husain asked him if he'd decided those families must "bear that pain".

Cameron replied: "What we've decided is that we're going to help those families in all the ways that we can."

He claimed the Institute for Fiscal Studies (IFS) review of the tax credit cuts, which concluded families would be worse off by up to £1,300 a year, did not take into account the increase in free childcare or the cuts in social rent.

But an IFS spokesperson said this morning that they hadn't taken those things into account because they wouldn't affect every claimant.

"Not everybody will have a three or four year old child," they said, before noting that most people claiming tax credits in social housing would have their rent paid with housing benefit - so the reduction in rent wouldn't affect them at all.

They said it doesn't affect their judgement that the mitigation from the increase in minimum wage is "partial".

Nightmare: Cameron got a rough ride on Today (Image: Rex)

"I think that was the old Labour way of doing things, that you have low rates of pay, you tax people, you give people back bits of money through the tax credit system and you use that to try and just get people over the line in terms of some artificial poverty measurement.

"I think far more meaningful is to go after the causes of poverty, get more people into work, get people off benefits, and have the chance of a good life and then let them earn a decent wage and then tax them less so that work really pays in our country. It's a very different way of going about tackling poverty."

Mr Cameron said "you don't help families if you lose control of your public finances, if you lose control of your welfare system, if you have unsustainable debts".

And the grilling didn't stop there.

Cameron was forced to agree with Theresa May's claim, which she'll make in a speech this morning, that building a cohesive society with mass immigration is "impossible."

David Cameron has had a stressful week at Tory party conference (Image: Getty)

He said "What she's saying - and I agree with this - is that if you have excessive levels of immigration it does become more difficult to build a cohesive society"

But Husain pressed him on May's use of the word "impossible."

He said "Yes", it was impossible. "Because, look. We have built the best and most proud multi-racial, multi-ethnic democracy in the world. I think we can be incredibly proud of that. But the point Theresa is making and the point I would make is that yes, we are an open economy, yes we welcome migrants to Britain, but it's easier to welcome people and integrate them if you can provide the school placew and the hospital beds and the strong community support. And that's more difficult if you have excessive levels of migration."

He stood accused of being comfortable with Assad staying in power during a transition in Syria, despite just two years ago calling for air strikes against his government for using chemical weapons against his own people.

He said: "Nothing has changed, my view has always been that Assad cannot play a part in Syria's future. He is the butcher of his own people, who has helped to create ISIL, who has been a recruiting sergeant for ISIL, and people who say "let's team up with Assad and take on ISIL", they don't understand that we need a Syria free of Assad and of ISIL.

But he wouldn't say how long he'd be comfortable with Assad staying in power. He said: "We haven't even started discussions, we need to start discussions about how transition is brought about."

He couldn't resist a pop at Jeremy Corbyn , opposed to air strikes in Syria, whom he said "I don't think, frankly, he sees what the ISIL risk is."